A known developing device includes seal members configured to contact both ends of a peripheral surface of a developer carrier. Specifically, the seal members are made of a urethane sponge and Teflon (trademark) felt affixed to the urethane sponge. The Teflon (trademark) felt contacts both ends of the peripheral surface of the developer carrier.
However, while the developer carrier rotates, a friction heat is generated between the developer carrier and the seal members, and the temperature of the friction heat gradually becomes high. Developer melts when the temperature exceeds the melting point of the developer. After the developer carrier is caused to stop rotating, the melt developer solidifies. The peripheral surface of the developer carrier may be sharpened by the solidified developer.